diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/devicetree/bindings/phy/samsung-phy.txt | 53 | ||||
| -rw-r--r-- | Documentation/phy/samsung-usb2.txt | 135 |
2 files changed, 188 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/phy/samsung-phy.txt b/Documentation/devicetree/bindings/phy/samsung-phy.txt index c0fccaa1671e..bf955abba5d9 100644 --- a/Documentation/devicetree/bindings/phy/samsung-phy.txt +++ b/Documentation/devicetree/bindings/phy/samsung-phy.txt @@ -20,3 +20,56 @@ Required properties: - compatible : should be "samsung,exynos5250-dp-video-phy"; - reg : offset and length of the Display Port PHY register set; - #phy-cells : from the generic PHY bindings, must be 0; + +Samsung S5P/EXYNOS SoC series USB PHY +------------------------------------------------- + +Required properties: +- compatible : should be one of the listed compatibles: + - "samsung,exynos4210-usb2-phy" + - "samsung,exynos4x12-usb2-phy" +- reg : a list of registers used by phy driver + - first and obligatory is the location of phy modules registers +- samsung,sysreg-phandle - handle to syscon used to control the system registers +- samsung,pmureg-phandle - handle to syscon used to control PMU registers +- #phy-cells : from the generic phy bindings, must be 1; +- clocks and clock-names: + - the "phy" clock is required by the phy module, used as a gate + - the "ref" clock is used to get the rate of the clock provided to the + PHY module + +The first phandle argument in the PHY specifier identifies the PHY, its +meaning is compatible dependent. For the currently supported SoCs (Exynos 4210 +and Exynos 4212) it is as follows: + 0 - USB device ("device"), + 1 - USB host ("host"), + 2 - HSIC0 ("hsic0"), + 3 - HSIC1 ("hsic1"), + +Exynos 4210 and Exynos 4212 use mode switching and require that mode switch +register is supplied. + +Example: + +For Exynos 4412 (compatible with Exynos 4212): + +usbphy: phy@125b0000 { + compatible = "samsung,exynos4x12-usb2-phy"; + reg = <0x125b0000 0x100>; + clocks = <&clock 305>, <&clock 2>; + clock-names = "phy", "ref"; + status = "okay"; + #phy-cells = <1>; + samsung,sysreg-phandle = <&sys_reg>; + samsung,pmureg-phandle = <&pmu_reg>; +}; + +Then the PHY can be used in other nodes such as: + +phy-consumer@12340000 { + phys = <&usbphy 2>; + phy-names = "phy"; +}; + +Refer to DT bindings documentation of particular PHY consumer devices for more +information about required PHYs and the way of specification. diff --git a/Documentation/phy/samsung-usb2.txt b/Documentation/phy/samsung-usb2.txt new file mode 100644 index 000000000000..ed12d437189d --- /dev/null +++ b/Documentation/phy/samsung-usb2.txt @@ -0,0 +1,135 @@ +.------------------------------------------------------------------------------+ +| Samsung USB 2.0 PHY adaptation layer | ++-----------------------------------------------------------------------------+' + +| 1. Description ++---------------- + +The architecture of the USB 2.0 PHY module in Samsung SoCs is similar +among many SoCs. In spite of the similarities it proved difficult to +create a one driver that would fit all these PHY controllers. Often +the differences were minor and were found in particular bits of the +registers of the PHY. In some rare cases the order of register writes or +the PHY powering up process had to be altered. This adaptation layer is +a compromise between having separate drivers and having a single driver +with added support for many special cases. + +| 2. Files description ++---------------------- + +- phy-samsung-usb2.c + This is the main file of the adaptation layer. This file contains + the probe function and provides two callbacks to the Generic PHY + Framework. This two callbacks are used to power on and power off the + phy. They carry out the common work that has to be done on all version + of the PHY module. Depending on which SoC was chosen they execute SoC + specific callbacks. The specific SoC version is selected by choosing + the appropriate compatible string. In addition, this file contains + struct of_device_id definitions for particular SoCs. + +- phy-samsung-usb2.h + This is the include file. It declares the structures used by this + driver. In addition it should contain extern declarations for + structures that describe particular SoCs. + +| 3. Supporting SoCs ++-------------------- + +To support a new SoC a new file should be added to the drivers/phy +directory. Each SoC's configuration is stored in an instance of the +struct samsung_usb2_phy_config. + +struct samsung_usb2_phy_config { + const struct samsung_usb2_common_phy *phys; + int (*rate_to_clk)(unsigned long, u32 *); + unsigned int num_phys; + bool has_mode_switch; +}; + +The num_phys is the number of phys handled by the driver. *phys is an +array that contains the configuration for each phy. The has_mode_switch +property is a boolean flag that determines whether the SoC has USB host +and device on a single pair of pins. If so, a special register has to +be modified to change the internal routing of these pins between a USB +device or host module. + +For example the configuration for Exynos 4210 is following: + +const struct samsung_usb2_phy_config exynos4210_usb2_phy_config = { + .has_mode_switch = 0, + .num_phys = EXYNOS4210_NUM_PHYS, + .phys = exynos4210_phys, + .rate_to_clk = exynos4210_rate_to_clk, +} + +- int (*rate_to_clk)(unsigned long, u32 *) + The rate_to_clk callback is to convert the rate of the clock + used as the reference clock for the PHY module to the value + that should be written in the hardware register. + +The exynos4210_phys configuration array is as follows: + +static const struct samsung_usb2_common_phy exynos4210_phys[] = { + { + .label = "device", + .id = EXYNOS4210_DEVICE, + .power_on = exynos4210_power_on, + .power_off = exynos4210_power_off, + }, + { + .label = "host", + .id = EXYNOS4210_HOST, + .power_on = exynos4210_power_on, + .power_off = exynos4210_power_off, + }, + { + .label = "hsic0", + .id = EXYNOS4210_HSIC0, + .power_on = exynos4210_power_on, + .power_off = exynos4210_power_off, + }, + { + .label = "hsic1", + .id = EXYNOS4210_HSIC1, + .power_on = exynos4210_power_on, + .power_off = exynos4210_power_off, + }, + {}, +}; + +- int (*power_on)(struct samsung_usb2_phy_instance *); +- int (*power_off)(struct samsung_usb2_phy_instance *); + These two callbacks are used to power on and power off the phy + by modifying appropriate registers. + +Final change to the driver is adding appropriate compatible value to the +phy-samsung-usb2.c file. In case of Exynos 4210 the following lines were +added to the struct of_device_id samsung_usb2_phy_of_match[] array: + +#ifdef CONFIG_PHY_EXYNOS4210_USB2 + { + .compatible = "samsung,exynos4210-usb2-phy", + .data = &exynos4210_usb2_phy_config, + }, +#endif + +To add further flexibility to the driver the Kconfig file enables to +include support for selected SoCs in the compiled driver. The Kconfig +entry for Exynos 4210 is following: + +config PHY_EXYNOS4210_USB2 + bool "Support for Exynos 4210" + depends on PHY_SAMSUNG_USB2 + depends on CPU_EXYNOS4210 + help + Enable USB PHY support for Exynos 4210. This option requires that + Samsung USB 2.0 PHY driver is enabled and means that support for this + particular SoC is compiled in the driver. In case of Exynos 4210 four + phys are available - device, host, HSCI0 and HSCI1. + +The newly created file that supports the new SoC has to be also added to the +Makefile. In case of Exynos 4210 the added line is following: + +obj-$(CONFIG_PHY_EXYNOS4210_USB2) += phy-exynos4210-usb2.o + +After completing these steps the support for the new SoC should be ready. |